U.S. patent application number 13/505086 was filed with the patent office on 2013-01-03 for machine with abradable ridges and method.
Invention is credited to Farshad Ghasripoor, Massimo Giannozzi, Lacopo Giovannetti, Dennis M. Gray, Vittorio Michelassi, Nuo Sheng.
Application Number | 20130004305 13/505086 |
Document ID | / |
Family ID | 42145024 |
Filed Date | 2013-01-03 |
United States Patent
Application |
20130004305 |
Kind Code |
A1 |
Giovannetti; Lacopo ; et
al. |
January 3, 2013 |
Machine with Abradable Ridges and Method
Abstract
A machine having a fixed part including a portion with a smooth
surface is provided. The machine also includes a rotating part
configured to rotate relative to the fixed part, the rotating part
directly facing the portion of the fixed part, and plural ridges
formed on the portion of the fixed part directly facing the
rotating part, the plural ridges comprising an abradable material,
wherein the abradable material is configured to be inoperable at
temperatures above about 1000.degree. C.
Inventors: |
Giovannetti; Lacopo;
(Florence, IT) ; Michelassi; Vittorio; (Muenchen,
DE) ; Giannozzi; Massimo; (Florence, IT) ;
Ghasripoor; Farshad; (Niskayuna, NY) ; Gray; Dennis
M.; (Niskayuna, NY) ; Sheng; Nuo; (Florence,
IT) |
Family ID: |
42145024 |
Appl. No.: |
13/505086 |
Filed: |
October 12, 2010 |
PCT Filed: |
October 12, 2010 |
PCT NO: |
PCT/US2010/052232 |
371 Date: |
September 12, 2012 |
Current U.S.
Class: |
415/196 |
Current CPC
Class: |
F05D 2250/181 20130101;
F05D 2250/184 20130101; F05D 2250/182 20130101; F05D 2250/183
20130101; F04D 29/162 20130101; F05D 2300/173 20130101; F01D 11/122
20130101; F05D 2300/17 20130101; F04D 29/023 20130101; F05D 2300/43
20130101; F05D 2300/434 20130101; F05D 2300/432 20130101; F04D
29/441 20130101 |
Class at
Publication: |
415/196 |
International
Class: |
F04D 29/44 20060101
F04D029/44 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 30, 2009 |
IT |
CO2009A000045 |
Claims
1. A machine comprising: a fixed part comprising a portion with a
smooth surface; a rotating part configured to rotate relative to
the fixed part, the rotating part directly facing the portion of
the fixed part; and plural ridges formed on the portion of the
fixed part directly facing the rotating part, the plural ridges
comprising an abradable material, wherein the abradable material is
configured to be inoperable at temperatures above about
1000.degree. C., wherein at least one ridge of the plural ridges is
curved.
2. The machine of claim 1, wherein the entire of at least one ridge
of the plural ridges is continuously curved.
3. The machine of claim 1, wherein all of the plural ridges are
continuously curved.
4. The machine of claim 1, wherein the plural ridges are configured
to be inoperable at temperatures above about 400.degree. C.
5. The machine of claim 1, wherein the abradable material is
plastic or metal based.
6. The machine of claim 5, wherein the plastic abradable material
comprises one or more of polytetrafluoroethylene (PTFE), polyimide
or Polyester.
7. The machine of claim 5, wherein the metallic abradable material
comprises one or more of AlSi, AlSi and Polyester, or
NiCrFeBNAl.
8. The machine of claim 1, wherein the abradable material covers a
region of the portion of the fixed part that spans one third or
less of an axial span of the rotating part.
9. The machine of claim 1, further comprising: a diaphragm
configured to enclose the rotating part, wherein the entire
diaphragm is made of the abradable material.
10. The machine of claim 1, wherein a cross section of at least one
ridge of the plural ridges is a rectangle or a triangle.
11. The machine of claim 10, wherein a height of the rectangular or
triangular ridges is between about 0.1 to about 0.5 mm.
12. The machine of claim 1, wherein the rotating part further
comprises: plural blades disposed on the rotating part, wherein
tips of the plural blades are configured to touch one or more of
the plural ridges when the rotating part rotates and wherein the
tips of the plural blades are not treated to include the abrasive
material.
13. The machine of claim 1, wherein the machine is an open shroud
centrifugal compressor and an operating temperature of the
centrifugal compressor is less than about 200.degree. C.
14. A diaphragm of a compressor, the diaphragm comprising: a fixed
part configured to accommodate at least an impeller of the
compressor and comprising a portion with a smooth surface; and an
abradable layer formed on the portion with the smooth surface of
the fixed part, wherein the abradable layer is machined to form
plural ridges directly facing the impeller, the plural ridges
comprising an abradable material, wherein the abradable material is
configured to be inoperable at temperatures above about
1000.degree. C., and wherein at least one ridge of the plural
ridges is continuously curved.
15. The diaphragm of claim 14, wherein the abradable material is
plastic or metal based.
17. The diaphragm of claim 15, wherein the plastic abradable
material comprises one or more of polytetrafluoroethylene (PTFE),
polyimide, or Polyester and the metallic abradable material
comprises one or more of AlSi, AlSi and Polyester, or
NiCrFeBNAl.
18. A method of depositing an abradable material on a diaphragm of
a machine, the method comprising: identifying in the diaphragm a
portion with a smooth surface that directly faces a rotating part
of the machine; depositing an abradable layer on the portion
directly facing the rotating part, the abradable layer comprising
an abradable material, wherein the abradable material is configured
to be inoperable at temperatures above about 1000.degree. C.; and
machining plural ridges in the abradable layer such that at least
one ridge of the plural ridges is curved.
19. The method of claim 18, further comprising: machining all of
the plural ridges to be continuously curved.
20. The method of claim 18, further comprising: preparing the
abradable material to be plastic or metal based, wherein the
plastic abradable material comprises one or more of
polytetrafluoroethylene (PTFE), polyimide, or Polyester and the
metallic abradable material includes one or more of AlSi, AlSi and
Polyester, or NiCrFeBNAl.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This is a national stage application under 35 U.S.C.
.sctn.371(c) of prior-filed, co-pending PCT patent application
serial number PCT/US2010/052232, filed on Oct. 12, 2010, which
claims priority to Italian Patent Application Serial No.
CO2009A000045, filed on Oct. 30, 2009, the entire contents of which
are incorporated herein by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] Embodiments of the subject matter disclosed herein generally
relate to methods and systems and, more particularly, to mechanisms
and techniques for producing abradable ridges in a machine having a
rotating part and a fixed part.
[0004] 2. Description of the Prior Art
[0005] Rotating machines, for example, gas turbines, used today in
various technical fields (power systems, petrochemical plants,
etc.) have at least a rotating part (rotor with blades) that
rotates with respect to a fixed part (shroud). A fluid is typically
injected at an input of the rotating machine to be
accelerated/pressurized and the fluid is then ejected at an outlet
of the rotating machine. Thus, a fluid flow is generated by the
rotating blades. For a good efficiency of the rotating machine, a
seal between the rotating part and the fixed part is desired to be
achieved so that most of the fluid flow is engaged by the blades of
the rotating part and does not leak over the tips of the blades,
which is unwanted leakage.
[0006] One way to provide the seal between the rotating part and
the fixed part of the rotating machine is to deposit an abradable
material on the fixed part so that the tips of the blades together
with the abradable material form a seal. If the abradable material
includes a ceramic, then an abrasive material may be provided on
tips of the blades of the rotating part to protect the tips when
contacting the abradable material to form the seal. Such a method
is described in U.S. Pat. No. 6,457,939, the entire content of
which is incorporated here by reference. U.S. Pat. No. 6,251,526,
the entire content of which is incorporated here by reference,
describes profiled abradable ceramic coating systems, in which a
porous ceramic coating is deposited onto a substrate with a
profiled surface, e.g., a metal grid brazed onto the substrate
surface (casing of the gas turbine) to form an abradable profiled
surface. Because the blades of the rotor of the turbine may
increase their size due to thermal expansion during the normal
operation of the turbine and/or due to centrifugal effects produced
by the high rotational speeds of the rotating part of the turbine
during operation, the blades may move towards the casing and may
remove part of the abradable material to achieve a smaller
clearance. The differential expansion rate between the rotating
part and the inner surface of the fixed part results in tips of the
blades contacting the abradable material to carve grooves in the
coating without contacting the casing itself. Thus, a custom-fitted
seal with minimal leakage is formed in the turbine. However, a
problem of such techniques is the grid brazed onto the substrate
(casing) of the turbine, which may result in damage to the shroud
upon profiling.
[0007] U.S. Pat. No. 6,887,528 and U.S. Patent Application
Publication No. 2005/0003172, both of which are assigned to the
assignee of the present patent application and the entire contents
of which are incorporated here by reference, disclose a method for
producing a profiled abradable coating on a casing of a gas turbine
without providing a grid on the casing of the turbine. The
abradable material includes a porous ceramic material that is able
to withstand temperatures as high as 1500.degree. C. The abradable
layer is formed on the casing by using direct-write technology or
plasma sprayed onto the substrate through a mask or a plasma gun.
However, this method uses expensive materials for the plural ridges
in order to withstand the high temperatures inside the gas
turbines.
[0008] For a better understanding of the background art, the
following example is discussed with regard to FIGS. 1 and 2. As
shown in FIG. 1, traditional methods for improving a clearance
between the tips of the blades and the fixed part of the turbine is
to machine in the casing 10 of the turbine a grid 11 by removing
part of the original material of the casing 10. Then, a thermal
barrier coating (TBC) layer 12 (i.e., a high temperature resistant
layer for protecting the casing from heat damage) is formed to not
be in direct contact with a surface 14 of the casing 10. An
abradable layer 16 is deposited on layer 12. A blade 18 of the
rotating part faces the abradable layer 16 and may scrape this
layer 16. As shown in FIG. 2, the abradable layer 16 and the TBC
layer 12 may be shaped as a ridge 20 having a straight-line shape
or ridge 22 having a zigzag shape. However, these traditional
methods for providing a high temperature resistant seal in the
turbines may be disadvantageous if used in other machines that do
not experience a high temperature because casing 10 may be damaged
when machining the grid 11 and/or may be expensive as the ceramic
abradable material requires exotic components, as for example,
yttria-stabilized zirconia.
[0009] Accordingly, it would be desirable to provide systems and
methods for providing an abradable material on machines that do not
operate in a high temperature environment.
BRIEF SUMMARY OF THE INVENTION
[0010] According to one exemplary embodiment, there is a machine
that includes a fixed part having a portion with a smooth surface;
a rotating part configured to rotate relative to the fixed part,
the rotating part directly facing the portion of the fixed part;
and plural ridges formed on the portion of the fixed part directly
facing the rotating part, the plural ridges being made of an
abradable material that is configured to be inoperable at
temperatures above about 1000.degree. C. At least one ridge of the
plural ridges is curved.
[0011] According to another exemplary embodiment, there is a
diaphragm of a compressor that includes a fixed part configured to
accommodate at least an impeller of the compressor and having a
portion with a smooth surface; and an abradable layer formed on the
portion with the smooth surface of the fixed part. The abradable
layer is machined to form plural ridges directly facing the
impeller, the plural ridges'being made of an abradable material
that is configured to be inoperable at temperatures above about
1000.degree. C., and at least one ridge of the plural ridges is
continuously curved.
[0012] According to still another exemplary embodiment, there is a
method of depositing an abradable material on a diaphragm of a
machine. The method includes identifying in the diaphragm a portion
with a smooth surface that directly faces a rotating part of the
machine; depositing an abradable layer on the portion directly
facing the rotating part, the abradable layer including an
abradable material that is configured to be inoperable at
temperatures above about 1000.degree. C.; and machining plural
ridges in the abradable layer such that at least one ridge of the
plural ridges is curved.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] The accompanying drawings, which are incorporated in and
constitute a part of the specification, illustrate one or more
embodiments and, together with the description, explain these
embodiments. In the drawings:
[0014] FIG. 1 is a schematic diagram of a portion of a conventional
gas turbine with an abradable material deposited on a grid formed
in the casing of the gas turbine;
[0015] FIG. 2 is a schematic diagram of a conventional pattern of
the abradable material of FIG. 1;
[0016] FIG. 3 is a schematic diagram of a compressor;
[0017] FIG. 4 is a schematic diagram of an impeller of the
compressor of FIG. 3;
[0018] FIG. 5 is a schematic diagram of a portion of a diaphragm of
a compressor according to an exemplary embodiment of the present
invention;
[0019] FIG. 6 is a schematic diagram of an abradable material
deposited on a diaphragm of a compressor according to an exemplary
embodiment of the present invention;
[0020] FIG. 7 is a schematic diagram of a pattern of plural ridges
formed in an abradable material according to an exemplary
embodiment of the present invention;
[0021] FIG. 8 is a schematic diagram of various ridge shapes that
can be formed according to an exemplary embodiment of the present
invention;
[0022] FIG. 9 is a schematic diagram of an interaction between
ridges and an impeller of a compressor according to an exemplary
embodiment of the present invention;
[0023] FIG. 10 is a schematic diagram of various layers that may be
formed on a diaphragm of a compressor according to an exemplary
embodiment of the present invention;
[0024] FIG. 11 is a graph showing advantages of curved patterns for
the ridges formed on a diaphragm according to an exemplary
embodiment of the present invention; and
[0025] FIG. 12 is a flow chart illustrating steps for forming the
plural ridges on the diaphragm of a machine according to an
exemplary embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0026] The following description of the exemplary embodiments
refers to the accompanying drawings. The same reference numbers in
different drawings identify the same or similar elements. The
following detailed description does not limit the invention.
Instead, the scope of the present invention is defined by the
appended claims. The following embodiments are discussed, for
simplicity, with regard to the terminology and structure of a
compressor. However, the embodiments to be discussed next are not
limited to compressors, but may be applied to other systems that
require a seal between a rotating part and a fixed part.
[0027] Reference throughout the specification to "one embodiment"
or "an embodiment" means that a particular feature, structure, or
characteristic described in connection with an embodiment is
included in at least one embodiment of the subject matter
disclosed. Thus, the appearance of the phrases "in one embodiment"
or "in an embodiment" in various places throughout the
specification is not necessarily referring to the same embodiment.
Further, the particular features, structures or characteristics may
be combined in any suitable manner in one or more embodiments.
[0028] FIG. 3 illustrates an open impeller centrifugal compressor
30. The open impeller centrifugal compressor 30 has an impeller 32
connected to a shaft 34. Shaft 34 may be supported by bearings 36
and 38. The impeller 32 has a hub portion 40 and a blade portion
42. A fluid enters the centrifugal compressor 30 at an inlet 44,
along an incoming direction A. The fluid reaches the impeller 32,
where it is accelerated based on the centrifugal force while
changing the fluid direction prior to being discharged at outlet 46
along direction B. A diaphragm 48, which faces the impeller 32, is
part of the fixed part of the compressor 30. The diaphragm may be
attached to a casing 49 of the compressor 30.
[0029] A detailed view of the impeller 32 is shown in FIG. 4. Other
structures for the impeller 32 may be used. The specific shape of
impeller 32 shown in FIG. 4 corresponds to an open impeller (no
element is covering blade portion 42). A centrifugal compressor
having this impeller is called an open impeller centrifugal
compressor. The blade portion 42 may have multiple blades 50 having
various contours, depending on the application/operation of the
compressor. These multiple blades 50 rotate inside the diaphragm 48
such that tips 52 of the blades 50 may move closer or even touch
the diaphragm 48 due to an elongation of the blades 50 because of
thermal transients, and/or the high rotational speed of the blades
50 relative to the diaphragm 48, and/or critical vibrations.
[0030] To prevent damages to the tips 52 of the blades 50 and also
to achieve a desirable seal between blade tips 52 and diaphragm 48,
as has been discussed in the Background of the Invention section,
an abrasive material may be coated on tips 52. However, no such
abrasive material is used in this exemplary embodiment. Thus, tips
52 of the blades 50 are vulnerable to damage if they contact the
strong material that the diaphragm 48 is made. For this reason, a
continuous layer of abradable material is deposited on a portion of
the diaphragm 48 that directly faces blades 50. This portion is
shown in FIG. 5 as element 60. According to another exemplary
embodiment, portion 60 may be smaller than shown in FIG. 5, i.e.,
may not extend the entire axial span of the blade portion 42.
According to this exemplary embodiment, portion 60 may be one third
of the axial span of the blade portion 42. In other words,
considering axis X as being parallel to the rotation axis of
impeller 32, the axial span of the blade portion 42 is between C
and F. The axial span of portion 60, which has the abradable
material thereon, may be between C and F or smaller, with the
smallest axial span being between E and F.
[0031] Another feature of the novel exemplary embodiments is that
the diaphragm 48, and more specifically, a surface 62 (see FIG. 5)
of the diaphragm 48 that receives the abradable material is smooth,
i.e., has no ridges, grids, or other formations intentionally
formed in the metal of the diaphragm 48. In one application, the
surface 62 of the portion 60 of the diaphragm 48, if represented in
a XY plane, with a longitudinal axis of the diaphragm 48 along axis
X, has a same sign of a partial derivative of a Y position with
respect to X along the longitudinal axis of the diaphragm 48
ignoring normal tolerances accepted in the industry for making such
large pieces of equipment. Further, even if small unevennesses are
present in the surface 62 of portion 60, if these are not
intentionally made, it is considered that the surface 62 is smooth.
This is different from some gas turbine shrouds that have ridges or
grids 11 intentionally formed in the casing 10 of the gas turbine
prior to depositing the abradable material 16, as shown in FIG.
1.
[0032] Another difference between the traditional gas turbines and
the novel embodiments is the temperature range. More specifically,
the gas turbines are known to operate at high temperatures, e.g.,
higher than about 1000.degree. C., while a compressor operates at
lower temperatures, in the range from about 100 to about
400.degree. C., and about 200.degree. C. for a centrifugal
compressor diaphragm. This large difference in the operation
temperature of a gas turbine and a compressor makes the ceramic
based abradable coatings of the traditional turbines not
suitable/unnecessary for compressors. Thus, other materials, as
will be discussed later, are used for coating the diaphragm of the
compressors.
[0033] According to an exemplary embodiment illustrated in FIG. 6,
the surface 62 of the diaphragm 48 may be directly covered with a
smooth layer 70 of an abradable material. The layer 70 of abradable
material may be directly deposited on the surface 62 of the
diaphragm 48, which is different from the gas turbine case in which
the TBC layer is formed on the casing prior to depositing the
abradable material. The direct formation of the abradable material
70 on the surface 62 of diaphragm 48 is possible because of the
lower temperature environment in which compressors operate.
[0034] Abradable materials to be used for compressors may be
divided into metallic-based abradable materials and plastic-based
abradable materials. These materials have a common property that
they are not designed to withstand high temperatures, as those
materials used in a gas turbine. In other words, the abradable
materials to be used in the compressors may become inoperable
(melt, peel, etc.) if used in the turbine of a gas turbine. In this
regard, the abradable materials to be used, for example, in
centrifugal compressors, are selected to operate at temperatures up
to about 200.degree. C. In another embodiment, depending on the
type of compressor, the abradable materials may operate at
temperatures up to about 400.degree. C. Metallic abradable
materials may include one or more of AlSi, AlSi and Polyester,
NiCrFeBNAl, etc. Plastic abradable materials may include one or
more of polytetrafluoroethylene (PTFE), Polyester, polyimide,
etc.
[0035] It is noted that the metallic and/or plastic abradable
material may be formed directly on the surface of the diaphragm 48,
without any protection layers (for example, TBC layers) as is
customary in the gas turbines. In this regard, a known ceramic
abradable material is not directly deposited on the substrate but
rather on a thermally resistant coating (layer 12 in FIG. 1), for
protecting the substrate (the casing) from the high temperatures
generated during the operation of the gas turbines. In another
exemplary embodiment, such thermally protective coatings may be
deposited on the diaphragm 48 prior to depositing the abradable
material 70.
[0036] After the abradable material 70 has been deposited on the
surface 62 of the diaphragm 48, the abradable material 70 may be
machined to form ridges 72 having peaks 74 and valleys 76 as shown
in FIG. 7. The shape of the ridges 72 may be diamond shape,
straight lines, constantly curved, continuously curved, etc. A
cross sectional view of ridges 72 is shown in FIG. 8. A shape of
ridge 72, as shown in the cross sectional view in FIG. 8, may have
a smooth shape as indicated by 80, or may have a triangular cross
section as indicated by 82, or may have a rectangular cross section
as indicated by 84, or other shapes. According to an exemplary
embodiment, the diaphragm 48 may be provided with a combination of
one or more of the above discussed shapes 80, 82, and 84. For
exemplary purposes, a dimension "d" of the ridges 72 may be between
about 0.0025 and about 0.102 mm for the rectangular shape and
between about 0 and about 0.102 mm for the triangular shape, and a
height "h" of the ridges 72 may be between about 0.1 and about 0.5
mm.
[0037] Once blades 50 are rotating with shaft 34 inside diaphragm
48, due to centrifugal effects and/or rotor unbalance and/or
thermal transients, the blades may move radially or axially towards
the diaphragm 48 to contact ridges 72. Depending on the degree of
expansion of the blades 50, tips 52 of the blades 50 may touch and
even break (remove) top parts of ridges 72 to form groove regions
90 as shown in FIG. 9. This close contact between ridges 72 and
blades 50 may achieve the desired sealing between the rotating part
and the fixed part of the compressor. In addition, the close
contact of the tips 52 of the blades 50 with ridges 72, which are
abradable and also have a soft structure due to their small
physical dimensions, prevents the tips 52 of the blades 50 to
suffer damages, given the fact that tips 52 have no protective
abrasive materials. In addition, if a thickness of the ridge 72 is
small, the material used to form the ridge may be dense.
[0038] According to another exemplary embodiment, the entire
diaphragm 48 may be made of the abradable material so that the
ridges 72 may be formed by machining the diaphragm 48 and not by
depositing abradable material.
[0039] A more detailed view of the layers deposited on the surface
62 of the diaphragm 48 according to an exemplary embodiment is
shown in FIG. 10. A bond coat layer 100 (for example, the bond coat
can be NiAl or NiCrAlY) having a height h1 of around 0.125 mm
optionally may be deposited on the diaphragm 48 by, for example,
plasma spray process. Optionally, a layer 102 of DVC-TBC (Dense
Vertically Cracked Thermal Barrier Coating) having a height h2 of
about 1.00 mm may be deposited over layer 100. The abradable layer
70 is formed over layer 102 or directly on layer 100 or directly on
diaphragm 48 and may have a height h3 of about 1.3 mm. Deviations
from these exemplary numbers in the range of 5% to 50% are also
possible.
[0040] Advantages of the novel abradable patterns discussed above
are now discussed with regard to FIG. 11. FIG. 11 shows the
variation of a total clearance reduction as a function of hot
running rubbed clearance for various abradable ridge shapes having
the same height. The hot running rubbed clearance is the actual
clearance between the impeller and the diaphragm when the impeller
rotates and the total clearance is the effective clearance due to
the shape of the ridges and other parameters. FIG. 11 illustrates
the relative effect of (i) abradable ridges with a curved pattern
(curve 124), (ii) abradable ridges with 45 degrees straight line
pattern (curve 122), and (iii) a smooth abradable layer with no
ridges and no pattern (curve 120). For a given hot clearance (e.g.,
102 mils, location 126 in FIG. 11), the abradable ridges with
curved pattern provide an advantage of approximately 18 mils
clearance reduction over the plural ridges with the straight line
pattern. The curved pattern may provide approximately 40 mils
clearance reduction over a compressor with no abradable layer
versus approximately 27 mils clearance for the straight line
pattern over the no abradable layer compressor. Curve 122
corresponds to plural ridges having a straight pattern inclined at
45 degrees relative to the axial direction of the compressor (see
for example FIG. 2, ridges 22) and curve 124 corresponds to plural
ridges having curved patterns (see for example FIG. 7, ridges 72).
It is noted that the curved patterns curve 124 provides a higher
clearance reduction (approximately 40 mils or 1 mm) than the
straight pattern curve 122 (clearance reduction approximately 27
mils or 0.68 mm) and the smooth abradable layer curve 120
(approximately 23 mils or 0.58 mm) for the same hot running rubbed
clearance 126. The total clearance reduction shown on the Y axis of
FIG. 11 indicates that for a same height of the ridges 72 of the
three curves 120, 122, and 124, the amount of fluid leaked between
the moving part and the fixed part of the compressor is smaller for
ridges 72 of curve 124 than for ridges 72 of curve 122. The shape
of the ridges (straight versus curved) generate this effect of
reduced clearance.
[0041] According to an exemplary embodiment, which is illustrated
in FIG. 12, there is a method for depositing an abradable material
on a diaphragm of a machine. The method includes a step 130 of
identifying in the diaphragm a portion with a smooth surface that
directly faces a rotating part of the machine; a step 132 of
depositing an abradable layer on the portion directly facing the
rotating part, the abradable layer including an abradable material
that is configured to be inoperable at temperatures above about
1000.degree. C.; and a step 134 of machining plural ridges in the
abradable layer such that at least one ridge of the plural ridges
is curved.
[0042] The disclosed exemplary embodiments provide a system and a
method for depositing an abradable material on a fixed part of a
machine having a moving part. However, the exemplary embodiments
are intended to cover alternatives, modifications and equivalents,
which are included in the spirit and scope of the invention as
defined by the appended claims. Further, in the detailed
description of the exemplary embodiments, numerous specific details
are set forth in order to provide a comprehensive understanding of
the claimed invention. However, one skilled in the art would
understand that various embodiments may be practiced without such
specific details.
[0043] Although the features and elements of the present exemplary
embodiments are described in the embodiments in particular
combinations, each feature or element can be used alone without the
other features and elements of the embodiments or in various
combinations with or without other features and elements disclosed
herein.
[0044] This written description uses examples of the subject matter
disclosed to enable any person skilled in the art to practice the
same, including making and using any devices or systems and
performing any incorporated methods. The patentable scope of the
subject matter is defined by the claims, and may include other
examples that occur to those skilled in the art. Such other example
are intended to be within the scope of the claims.
* * * * *